1) Field of the Invention
The present invention relates to an auxiliary punching device attachable to a machine for punching holes at one given location into a stack of sheets of given size, which device permits to punch other holes at another given location in the same stack at the very same time as the holes are punched at the one location.
b) Brief Description of the Prior Art
Machines for punching holes into a stack of paper are well known and commonly used in the printing industry for different purposes such as, for example, punching a row of equally spaced apart holes along one of the vertical edges of the pages of a diary or of a calendar to make these pages connectable to each other by mere insertion into the holes of a coil-shaped metal binding.
For some particular applications such as the manufacture of diaries with detachable corners or tabs, or of booklets of coupons, it is often necessary to punch at least one other row of holes into the same pages, this other row often extending in a different direction and being made of holes of different size.
In practice, this has been done so far in three different ways.
The first one which is the most widely used, consists in passing the stack of pages to be punched through the punching machine to punch the first row of holes, then replacing the original die and punching tool assembly of this machine by another different one and finally passing again the same stack of pages into the machine to punch the other row of holes using the other die and punching tool assembly to do so.
As can be understood, this first method is time consuming as it requires to pass each stack twice into the same machine, with the risk of errors that may result from such a manipulation.
A second way of punching two rows of holes into a stack of sheets consists in manufacturing a custom-made die and punching tool assembly capable of punching these two rows and mounting this custom-made assembly onto the punching machine in lieu of the original assembly. This second method is efficient but very expensive.
A third way of punching two rows of boles into a stack of sheets that has apparently been tried by some printers, consists in attaching an auxiliary die and punching tool assembly to the die and punching tool assembly in such a manner that both assemblies work in unisson. This third method is efficient and not very expensive. However, to the Applicant's knowledge, noone has devised so far an auxiliary punching device of this type that is really adjustable to fit any required positioning and configuration for the second row of holes, or any size of sheets of paper to be punched.